In addition to mounds, gopher burrows have plugged openings where a gopher has come to the surface, probably to cut plants. Such entrances are marked by a plug of earth several inches long. Mounds and feeding entrances of the gopher burrow are usually not constructed in the main burrow system itself, but at the ends of lateral burrows of varying length. If one traces the burrow back from the mound, a junction with the main, better-constructed burrow is found. The junction is usually T-shaped, with the lateral burrow at right angles to the main burrow. More rarely the junction has a Y-shape. [Illustration: FIG. 96. Giant mounds raised by pocket gophers on Mima Prairie, Thurston County, Washington, July 13, 1941. (Fish and Wildlife Service photo by Victor B. Scheffer, No. 1209.)] The burrow system of the pocket gopher may be divided into three main parts. These are the laterals, just discussed, the main burrow, and the deep nesting burrow. The main burrow is a sinuous tube or tunnel at a relatively uniform depth, that marks the extent of the gopher's home territory. This tunnel may branch, or even intersect. As it is extended in one direction, the earth excavated by the gopher may in part be thrust into an unused portion of the burrow. The deep, nesting burrows may be used only in the breeding season. They are connected with the main tunnel system but descend to a greater depth. Usually they descend into the harder, consolidated layers of soil below the zone where plant roots penetrate. Here chambers are constructed in which nests and food are stored. Usually a vertical shaft is dug in the burrow ahead of the nest to lead rain water away from the nest.